In 3GPP (3rd Generation Partnership Project) which is a project aiming to standardize a mobile communication system, the introduction of Device to Device (D2D) proximity service is discussed as a new function after Release 12 (see Non Patent Document 1).
The D2D proximity service (D2D ProSe) is a service enabling direct Device-to-Device communication within a synchronization cluster including a plurality of synchronized user terminals. The D2D proximity service includes a D2D discovery procedure (Discovery) in which a proximal terminal is discovered and D2D communication (Communication) that is direct Device-to-Device communication.
In order to make a D2D proximity service available while decreasing a load of a base station, it is assumed that a transmission-side user terminal that transmits user data in D2D communication transmits scheduling assignment information (SA: Scheduling Assignment) indicating a time-frequency location of a D2D data resource used for receiving the user data.